Summary from Rob's book : Modulating the Flavor Profile of Coffee

Modulating the flavor of coffee has been a pursuit for every roaster. It is never ending. We thought we have got it but, no. It is never ending.

Over the past few months we have been busy in procuring beans from all over the world. In our collection now, we have about 30 different types of coffee from various origin. Those are the ones that we have listed, but in actual fact, more are on the shelves that is seen as a hard roast/sensitive we put it aside as KIV.

We have been roasting a number of Ethiopian, not many South American but we are moving towards that. We start to fell in love with central American beans, especially the SHB Guatemalan coffee and Honduran. Indonesian beans about 4-5 types. With various experimental processing that is available on the market, we are still finding and making improvements on our roasting technique in getting the best out of every cup for all the coffee that we have on offer.

Apart from roasting and procuring coffee, we have been doing a lot of reading the technicalities of roasting from the infamous Rob Hoos and Scott Rao's books. There are not much books available on roasting. Im guessing, man hours plays a very important role. That includes cupping and roasting.

While writing the book, Rob Hoos was at his 7200 roasts and counting. Assuming each roast is about 10 minutes, that accumulates to 1200 hours or about 50 days of roasting non stop.

After reading the two books and reading various forums, there were a lot of thoughts. Particularly on how these two roasters think.

Scott Rao's book was focusing and helping on how a roaster should understand their machine works better. His book was well written. Easy to understand and complete. The whole idea was to obtain a smooth declining rate of rise (ROR) during roasting.

"It is easy," according to Scott, "but the hard part was to understand how your machine would react to certain changes that was made during roasting.". He is right, different beans react differently to heat and pressure and airflow. The process is the same though, there's the charge temperature (CHARGE), theres the dry-end phase (DRY), there's first crack (FC), there's end of first crack (FC-END), theres development time % (DTR) and at what point do you exit (DROP) your roast.

Different beans would have different water moisture. It also have different density and sized differently. With different process of processing the coffee, the moisture of the dried beans would differ. Its terroir also would impact the point when do you make changes on the roasting process. In other words, when do you increase or decrease the fan or increase or reduce the flame? Each changes would definitely have an impact towards obtaining a flick-free roast profile or a smooth declining ROR. Scott argued that no matter what machine are we using (both our roaster are drum roaster), the importance it is to know what are the impact when drum speed is reduced or increased, when the fan is reduced or increased or when the firing pressure is increased or decreased. It is the hardest part. This is because the margin that may affect the taste is could be in milli second.

Still trying to achieve a minimal flick while roasting Natural Taba Supreme (Rwanda)

Is it important to obtain a flick free roast? To us, we as a guideline how we should control our roasting machine and to formulate a roast profile. There are way too many variables that affect the cup. 

As argued by Scott's book earlier "margin that may affect taste could be by the milli second". Rob Hoos book was all about the margins that may affect the flavour. He talked about the changes during DE, changes during Maillard phase and changes during the %DTR. In great detail. 

Caramelization is something new to us. We thought that Caramelization is during maillard phase. But in actual fact, the degree of the drop temperature. Sucrose are the main cause of FC. At a lower degree of drop temperature (say 203C), the cup may be sweet and full of aromatics, but if its dropped say at 207C the sweetness may turn to maple syrupy (still sweet) but lack of aromatics. As it get higher or even lower, the taste will change. It is stated in the books that, roaster are not the creator of flavours. Their function is like a pilot. Bringing in the right notes/sweet spot of the coffee to the cup. 

After reading the book, we did quite a number of roast on how would different drop temperature change the sweetness of the cup. We also found that, when the drop temperature is high, but the %DTR is lower, the aromatics MAY still be very bright.

From the Roasting forums online, many roasters kill of the fire once they heard the first crack. Some beans crack at 198C, some beans at 202 and some at 204C. But towards the end of the roast, the ROR of the coffee has already gone down to a minimum and smoke has already come out from the beans, most likely a roaster would induced a high airflow to remove the smoke from the coffee to eliminate smokiness flavour on the coffee. But with high airflow and without fire power, the BT and the ET will reduce and halt the caramelisation process. Its a very tricky situation.

Some of the things we ponder a lot after reading the book. But it gives a better confidence and clear understanding on the phases that involves during roasting. 

The whole concept is similar to the concept of opportunity cost when it comes to money or identifying the point of the diminishing returns in economics. Really an interesting concept. 

We call it the economics of coffee flavour.